There is an immediate need for pharmacological agents to potently and effectively modulate specific epigenetic enzymes and effector molecules. We have designed, established and successfully used a mammalian cell- based assay to identify chemical modulators of epigenetic pathways using a broad rather than a target specific approach to maximize the mechanistic diversity of assay actives. Using this assay we have recently conducted quantitative HTS using a titration-response method to evaluate more than 300,000 diverse compounds at multiple doses. We have identified and independently confirmed more than 70 actives. Evaluation of the anti- cancer potential of one of these hits, uncovered that this drug selectively targets lung cancer cells blocking their growth and triggering their cell death, without affecting normal human bronchial epithelial cells. This compound alters transcriptional pathways and affects epigenetic modifications of histones. In vivo, it shows anti-tumor activity in mouse xenografts. Our goal now is to characterize this top hit, which we call Drug 4, determining the epigenetic events and genomic sites it modifies, defining the mechanism of its anti-growth/anti- cancer activity and identifying the cellular proteins it targets, and in this way, to set up a pipeline through which we can characterize our other hits in future studies. We will use pairs of matched cell lines derived from the normal and the cancerous lung of patients to characterize the effects of this compound on the physiological vs. the pathological epigenomic/transcriptional landscape through the following aims: 1.Measure the effects of Drug 4 in normal vs. cancer cells on the expression level of genes that control cell proliferation pathways and evaluate epigenetic marks in cancer cells and in tumors at a subset of these loci selectively altered by Drug 4 in cancer. We will measure levels of genes that regulate cell growth/cell death pathways to identify those selectively affected by our drug in cancer but not in normal cells. We will then define drug 4-induced changes in epigenetic marks at the promoters of a subset of these genes. 2.Define the mechanism of Drug 4 induced growth inhibition/cancer cell death, in cells and in tumors. We will investigate if the cancer-specific cell cycle arrest & cell death triggered by Drug 4 depend on the cyclin D3/Rb pathway & the Egln3/KIF1B pathways, respectively, as suggested by preliminary results. 3.Identify the cellular targets of our compound through candidate molecule and unbiased approaches. We will determine the effect of Drug 4 on the activity of purified epigenetic enzymes and effector molecules to identify compound targets. We will perform biotinylated-drug pull downs and siRNA screens if needed. These aims will help us elucidate the mechanism of action of Drug 4, and in particular, its selectivity against cancer. The studies proposed here will also lay the foundation for the future characterization and development of the other potential epigenetic modulators we have already identified. These compounds will have significant impact on basic research and on clinical therapeutic development for many pathologies, including cancer. PUBLIC HEALTH RELEVANCE: We have identified a drug that shuts down genes that foster uncontrolled cell growth and turns on genes that slow down tumor growth. This compound shows the ability to specifically kill cancer cells and to decrease tumor size in mice, without affecting normal cells. Here, we propose to define how this drug works and to further develop it for therapeutic applications.